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We report the magnetic properties of newly synthesized, single crystals of $\mathrm{TbTi_3Bi_4}$ whose crystal structure is highlighted by the stacking of terbium-based zigzag chains and titanium-based kagome lattices. This compound demonstrates extreme easy-axis magnetic anisotropy due to the crystalline-electric-field effect which aligns the $\mathrm{Tb^{3+}}$ moments along the zigzag chain direction. As the result of the strong single-ion anisotropy and multiple magnetic interactions, $\mathrm{TbTi_3Bi_4}$ behaves as a quasi-one-dimensional Ising magnet with a remarkable antiferromagnetic ordering at $T_\mathrm{N}$ = 20.4 K. When a magnetic field is applied along the direction of the zigzag chain, multiple meta-magnetic transitions occur between 1/3 and other magnetization plateaus. We have created a field-temperature phase diagram and mapped out the complex magnetic structures resulting from frustration.
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https://arxiv.org/abs/2405.09280v1
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We address a longstanding question of whether ABJM theory has Wilson loop operators preserving eight supercharges (so 1/3 BPS). We present such Wilson loops made of a large supermatrix combining two 1/2 BPS Wilson loops. We study the spectrum of operator insertions into them including the displacement operator and several others and study their correlation functions. Another natural construction arising in this context are Wilson loops with alternating superconnections. This amounts to including "defect changing operators" along the loop, similar to a discrete cusp. This insertion is topological and preserves two supercharges. We study the multiplet of this operator and how it can be used to introduce further operators. We also construct the defect conformal manifold arising from marginal defect operators.
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https://arxiv.org/abs/2212.03886v2
|
We present the first detection of the 13C17O J=3-2 transition toward the HL
Tau protoplanetary disc. We find significantly more gas mass (at least a factor
of ten higher) than has been previously reported using C18O emission. This
brings the observed total disc mass to 0.2 M, which we consider to be a
conservative lower limit. Our analysis of the Toomre Q profile suggests that
this brings the disc into the regime of gravitational instability. The radial
region of instability (50-110 au) coincides with the location of a proposed
planet-carved gap in the dust disc and a spiral in the gas. We, therefore,
propose that if the origin of the gap is confirmed to be due to a forming giant
planet, then it is likely to have formed via the gravitational fragmentation of
the protoplanetary disc.
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http://arxiv.org/abs/2001.07550v1
|
Color-center-hosting semiconductors are emerging as promising source
materials for low-field dynamic nuclear polarization (DNP) at or near room
temperature, but hyperfine broadening, susceptibility to magnetic field
heterogeneity, and nuclear spin relaxation induced by other paramagnetic
defects set practical constraints difficult to circumvent. Here, we explore an
alternate route to color-center-assisted DNP using nitrogen-vacancy (NV)
centers in diamond coupled to substitutional nitrogen impurities, the so-called
P1 centers. Working near the level anti-crossing condition - where the P1
Zeeman splitting matches one of the NV spin transitions - we demonstrate
efficient microwave-free 13C DNP through the use of consecutive magnetic field
sweeps and continuous optical excitation. The amplitude and sign of the
polarization can be controlled by adjusting the low-to-high and high-to-low
magnetic field sweep rates in each cycle so that one is much faster than the
other. By comparing the 13C DNP response for different crystal orientations, we
show that the process is robust to magnetic field/NV misalignment, a feature
that makes the present technique suitable to diamond powders and settings where
the field is heterogeneous. Applications to shallow NVs could capitalize on the
greater physical proximity between surface paramagnetic defects and outer
nuclei to efficiently polarize target samples in contact with the diamond
crystal.
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http://arxiv.org/abs/1909.06642v1
|
Nuclear hyperpolarization is a known method to enhance the signal in nuclear magnetic resonance (NMR) by orders of magnitude. The present work addresses the $^{13}$C hyperpolarization in diamond micro- and nanoparticles, using the optically-pumped nitrogen-vacancy center (NV) to polarize $^{13}$C spins at room temperature. Consequences of the small particle size are mitigated by using a combination of surface treatment improving the $^{13}$C relaxation ($T_1$) time, as well as that of NV, and applying a technique for NV illumination based on a microphotonic structure. Monitoring the light-induced redistribution of the NV spin state populations with electron paramagnetic resonance, a strong polarization enhancement for the NV spin state is observed in a narrow spectral region corresponding to about 4\% of these defect centers. By combining adjustments to the `PulsePol' sequence and slow sample rotation, the NV-$^{13}$C polarization transfer rate is improved further. The hyperpolarized $^{13}$C NMR signal is observed in particles of 2 $\mu$m and 100 nm median sizes, with enhancements over the thermal signal (at 0.29 T magnetic field), of 1500 and 940, respectively. The present demonstration of room-temperature hyperpolarization anticipates the development of agents based on nanoparticles for sensitive magnetic resonance applications.
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https://arxiv.org/abs/2403.14521v2
|
We have carried out observations of CCH and its two $^{13}$C isotopologues,
$^{13}$CCH and C$^{13}$CH, in the 84 - 88 GHz band toward two starless cores,
L1521B and L134N (L183), using the Nobeyama 45 m radio telescope. We have
detected C$^{13}$CH with a signal-to-noise (S/N) ratio of 4, whereas no line of
$^{13}$CCH was detected in either the dark clouds. The column densities of the
normal species were derived to be ($1.66 \pm 0.18$)$\times 10^{14}$ cm$^{-2}$
and ($7.3 \pm 0.9$)$\times 10^{13}$ cm$^{-2}$ ($1 \sigma$) in L1521B and L134N,
respectively. The column density ratios of $N$(C$^{13}$CH)/$N$($^{13}$CCH) were
calculated to be $>1.1$ and $>1.4$ in L1521B and L134N, respectively. The
characteristic that $^{13}$CCH is less abundant than C$^{13}$CH is likely
common for dark clouds. Moreover, we find that the $^{12}$C/$^{13}$C ratios of
CCH are much higher than those of HC$_{3}$N in L1521B by more than a factor of
2, as well as in Taurus Molecular Cloud-1 (TMC-1). In L134N, the differences in
the $^{12}$C/$^{13}$C ratios between CCH and HC$_{3}$N seem to be smaller than
those in L1521B and TMC-1. We discuss the origins of the $^{13}$C isotopic
fractionation of CCH and investigate possible routes that cause the
significantly high $^{12}$C/$^{13}$C ratio of CCH especially in young dark
clouds, with the help of chemical simulations. The high $^{12}$C/$^{13}$C
ratios of CCH seem to be caused by reactions between hydrocarbons (e.g., CCH,
C$_{2}$H$_{2}$, $l,c$-C$_{3}$H) and C$^{+}$.
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http://arxiv.org/abs/1908.09983v1
|
We observed the $J=5-4$ rotational lines of the normal species and three
$^{13}$C isotopologues of HC$_{3}$N at the 45 GHz band toward two low-mass
starless cores, L1521B and L134N (L183), using the Nobeyama 45 m radio
telescope in order to study the main formation pathways of HC$_{3}$N in each
core. The abundance ratios of the three $^{13}$C isotopologues in L1521B are
derived to be [H$^{13}$CCCN]:[HC$^{13}$CCN]:[HCC$^{13}$CN] = 0.98 (+- 0.14) :
1.00 : 1.52 (+- 0.16) (1 sigma). The fractionation pattern is consistent with
that at the cyanopolyyne peak in Taurus Molecular Cloud-1. This fractionation
pattern suggests that the main formation pathway of HC$_{3}$N is the
neutral-neutral reaction between C$_{2}$H$_{2}$ and CN. On the other hand,
their abundance ratios in L134N are found to be
[H$^{13}$CCCN]:[HC$^{13}$CCN]:[HCC$^{13}$CN]= 1.5 (+- 0.2) : 1.0 : 2.1 (+- 0.4)
(1 sigma), which are different from those in L1521B. From this fractionation
pattern, we propose that the reaction between HNC and CCH is a possible main
formation pathway of HC$_{3}$N in L134N. We find out that the main formation
pathways of the same molecule are not common even in the similar physical
conditions. We discuss the possible factors to make a difference in
fractionation pattern between L134N and L1521B/TMC-1.
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http://arxiv.org/abs/1707.08267v1
|
We present the first determination of the abundance ratios of $^{13}$C substitutions of cyanoacetylene (HC$_{3}$N), [H$^{13}$CCCN]:[HC$^{13}$CCN]:[HCC$^{13}$CN] in Titan's atmosphere measured using millimeter-wave spectra obtained by the Atacama Large Millimeter-submillimeter Array. To compare the line intensities precisely, datasets which include multiple molecular lines were extracted to suppress effects of Titan's environmental conditions and observation settings. The [HC$^{13}$CCN]:[HCC$^{13}$CN] and [H$^{13}$CCCN]:[HCC$^{13}$CN}] ratios were obtained from 12 and 1 selected datasets, respectively. As a result, nearly the uniform [H$^{13}$CCCN]:[HC$^{13}$CCN]:[HCC$^{13}$CN] abundance ratios as 1.17 ($\pm$0.20) : 1.09 ($\pm$0.25) : 1 (1$\sigma$) were derived, whereas previously reported ratios for interstellar medium (ISM) have shown large anomalies that may be caused by $^{13}$C concentrations in precursors. The result obtained here suggests that $^{13}$C concentration processes suggested in the ISM studies do not work effectively on precursors of HC$_{3}$N and HC$_{3}$N itself due to Titan's high atmospheric temperature and/or depletion of both $^{13}$C and $^{13}$C$^+$.
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https://arxiv.org/abs/2108.05019v1
|
We investigated the local magnetism of the organic conductor, $\kappa$-(ET)$_{2}$Hg(SCN)$_{2}$Cl, with a quasi-triangular lattice of weakly dimerized molecules through $^{13}$C NMR spectroscopy. The NMR spectra and nuclear relaxation show that charge disproportionation occurs, associated with the metal-insulator transition at 31 K. The relaxation rate indicates that the paramagnetic spins in the insulating phase undergo a transition into a spin-singlet ground state with the emergence of orphan spins, a possible valence-bond-glass state. The present results are in high contrast to the spin-cluster paramagnetism of the electric dipole-liquid candidate, $\kappa$--(ET)$_{2}$Hg(SCN)$_{2}$Br, having nearly identical material parameters. This fact indicates that these two systems are on the verge between distinct phases in both charge and spin degrees of freedom; a spin-singlet charge-ordered state versus a spin-active Mott insulating state, competing with each other on a triangular lattice of dimerized sites.
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https://arxiv.org/abs/2310.08963v2
|
In dense clouds of the interstellar medium, dust grains are covered by ice
mantles, dominated by H$_2$O. CO and CO$_2$ are common ice components observed
in infrared spectra, while infrared inactive N$_2$ is expected to be present in
the ice. Molecules in the ice can be dissociated, react or desorb by exposure
to secondary ultraviolet photons. Thus, different physical scenarios lead to
different ice mantle compositions. This work aims to understand the behaviour
of $^{13}$CO : N$_2$ and $^{13}$CO$_2$ : N$_2$ ice mixtures submitted to
ultraviolet radiation in the laboratory. Photochemical processes and
photodesorption were studied for various ratios of the ice components.
Experiments were carried out under ultra-high vacuum conditions at 12K. Ices
were irradiated with a continuous emission ultraviolet lamp simulating the
secondary ultraviolet in dense interstellar clouds. During the irradiation
periods, fourier-transform infrared spectroscopy was used for monitoring
changes in the ice, and quadrupole mass spectrometry for gas-phase molecules.
In irradiated $^{13}$CO$_2$ : N$_2$ ice mixtures, $^{13}$CO, $^{13}$CO$_2$,
$^{13}$CO$_3$, O$_2$, and O$_3$ photoproducts were detected in the infrared
spectra. N$_2$ molecules also take part in the photochemistry, and N-bearing
molecules were also detected: NO, NO$_2$, N$_2$O, and N$_2$O$_4$.
Photodesorption rates and their dependence on the presence of N$_2$ were also
studied. As it was previously reported, $^{13}$CO and $^{13}$CO$_2$ molecules
can transfer photon energy to N$_2$ molecules. As a result, $^{13}$CO and
$^{13}$CO$_2$ photodesorption rates decrease as the fraction of N$_2$
increases, while N$_2$ photodesorption is enhanced with respect to the low
UV-absorbing pure N$_2$ ice.
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http://arxiv.org/abs/1903.11906v1
|
Strongly squeezed light at telecommunication wavelengths is the necessary
resource for one-sided device-independent quantum key distribution via fibre
networks. Reducing the optical pump power that is required for its generation
will advance this quantum technology towards efficient out-of-laboratory
operation. Here, we investigate the second-harmonic pump power requirement for
parametric generation of continuous-wave squeezed vacuum states at 1550nm in a
state-of-the-art doubly-resonant standing-wave PPKTP cavity setup. We use
coarse adjustment of the Gouy phase via the cavity length together with
temperature fine-tuning for simultaneously achieving double resonance and
(quasi) phase matching, and observe a squeeze factor of 13dB at 1550nm from
just 12mW external pump power at 775nm. We anticipate that optimizing the
cavity coupler reflectivity will reduce the external pump power to 3mW, without
reducing the squeeze factor.
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http://arxiv.org/abs/2005.09891v1
|
We present in this paper a 4-dimensional formulation of the Newton equations
for gravitation on a Lorentzian manifold, inspired from the 1+3 and 3+1
formalisms of general relativity. We first show that the freedom on the
coordinate velocity of a general time-parametrised coordinate system with
respect to a Galilean reference system is similar to the shift freedom in the
3+1-formalism of general relativity. This allows us to write Newton's theory as
living in a 4-dimensional Lorentzian manifold $M^N$. This manifold can be
chosen to be curved depending on the dynamics of the Newtonian fluid. In this
paper, we focus on a specific choice for $M^N$ leading to what we call the
\textit{1+3-Newton equations}. We show that these equations can be recovered
from general relativity with a Newtonian limit performed in the rest frames of
the relativistic fluid. The 1+3 formulation of the Newton equations along with
the Newtonian limit we introduce also allow us to define a dictionary between
Newton's theory and general relativity. This dictionary is defined in the rest
frames of the dust fluid, i.e. a non-accelerating observer. A consequence of
this is that it is only defined for irrotational fluids. As an example
supporting the 1+3-Newton equations and our dictionary, we show that the
parabolic free-fall solution in 1+3-Newton exactly translates into the
Schwarzschild spacetime, and this without any approximations. The dictionary
might then be an additional tool to test the validity of Newtonian solutions
with respect to general relativity. It however needs to be further tested for
non-vacuum, non-stationary and non-isolated Newtonian solutions, as well as to
be adapted for rotational fluids. One of the main applications we consider for
the 1+3 formulation of Newton's equations is to define new models suited for
the study of backreaction and global topology in cosmology.
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http://arxiv.org/abs/2010.10247v1
|
We present the first resolved observations of the 1.3mm polarized emission
from the disk-like structure surrounding the high-mass protostar Cepheus A HW2.
These CARMA data partially resolve the dust polarization, suggesting an uniform
morphology of polarization vectors with an average position angle of 57 degrees
and an average polarization fraction of 2.0%. The distribution of the
polarization vectors can be attributed to (1) the direct emission of
magnetically aligned grains of dust by a uniform magnetic field, or (2) the
pattern produced by the scattering of an inclined disk. We show that both
models can explain the observations, and perhaps a combination of the two
mechanisms produce the polarized emission. A third model including a toroidal
magnetic field does not match the observations. Assuming scattering is the
polarization mechanism, these observations suggest that during the first few
10000 years of high-mass star formation, grain sizes can grow from 1 to several
10s micron.
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http://arxiv.org/abs/1610.03407v1
|
We point out that the quantum Grad's 13-moment system [R. Yano, Physica A:
Statistical Mechanics and its Applications, 416:231-241, 2014] is lack of
global hyperbolicity, and even worse, the thermodynamic equilibrium is not an
interior point of the hyperbolicity region of the system. To remedy this
problem, by fully considering Grad's expansion, we split the expansion into the
equilibrium part and the non-equilibrium part, and propose a regularization for
the system with the help of the new theory developed in [Z. Cai et al., SIAM J.
Appl. Math., 75(5):2001-2023, 2015, Y. Fan, J. Stat. Phys., 161(4), 2015]. This
provides us a new model which is hyperbolic for all admissible thermodynamic
states, and meanwhile preserves the approximate accuracy of the original
system. It should be noted that this procedure is not a trivial application of
the theory in [Z. Cai et al., SIAM J. Appl. Math., 75(5):2001-2023, 2015, Y.
Fan, J. Stat. Phys., 161(4), 2015].
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http://arxiv.org/abs/1607.00175v2
|
Using the EXOplanet Transit Interpretation Code (EXOTIC), we reduced 52 sets of images of WASP-104 b, a Hot Jupiter-class exoplanet orbiting WASP-104, in order to obtain an updated mid-transit time (ephemeris) and orbital period for the planet. We performed this reduction on images taken with a 6-inch telescope of the Center for Astrophysics | Harvard & Smithsonian MicroObservatory. Of the reduced light curves, 13 were of sufficient accuracy to be used in updating the ephemerides for WASP-104 b, meeting or exceeding the three-sigma standard for determining a significant detection. Our final mid-transit value was 2457805.170208 +/- 0.000036 BJD_TBD and the final period value was 1.75540644 +/- 0.00000016 days. The true significance of our results is in their derivation from image sets gathered over time by a small, ground-based telescope as part of the Exoplanet Watch citizen science initiative, and their competitive results to an ephemeris generated from data gathered by the TESS telescope. We use these results to further show how such techniques can be employed by amateur astronomers and citizen scientists to maximize the efficacy of larger telescopes by reducing the use of expensive observation time. The work done in the paper was accomplished as part of the first fully online Course-Based Undergraduate Research Experience (CURE) for astronomy majors in the only online Bachelor of Science program in Astronomical and Planetary Sciences.
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https://arxiv.org/abs/2306.17251v1
|
We report the high-pressure optical floating-zone growth of GdInO$_3$ single crystals and show its magnetic phase diagram down to the mK-regime as determined by magnetization measurements. The centered-honeycomb lattice structure shows considerable magnetic frustration ($\lvert\Theta\rvert /T_{\rm N}\simeq 5$) and develops long-range magnetic order below $T_{\rm N}$~=~2.1 K from a short-range ordered paramagnetic phase. Concomitantly, a small net magnetic moment evolves at $T_{\rm N}$ which points along the crystallographic $c$ direction. Upon cooling, the net moment reorients at $T^{**}\simeq 1.7$ K and $T^{*}\simeq 1$ K. A broad 1/3 plateau indicative of the up-up-down ($uud$) spin configuration appears for $B||c$ but is absent for $B||ab$, thereby suggesting easy axis anisotropy. At $T=0.4$ K, a jump in magnetization at $\simeq 3/5$ of the saturation magnetization signals a discontinuous transition to a high field phase and we find evidence for a possible tricritical point. Small energy and field scales in the accessible regimes render GdInO$_3$ a prime example to study the phase diagram of a semiclassical frustrated hexagonal lattice in the presence of weak easy axis anisotropy of mainly dipolar origin.
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https://arxiv.org/abs/2308.04935v1
|
Fast Abstracts are short presentations of work in progress or opinion pieces
and aim to serve as a rapid and flexible mechanism to (i) Report on current
work that may or may not be complete; (ii) Introduce new ideas to the
community; (iii) State positions on controversial issues or open problems.
Student Forum is a vibrant and friendly environment where students can present
their work, exchange ideas and experiences, get feedback on their work, get new
inspirations and points of view. In addition, the forum stimulates interaction
between young researchers, experienced researchers, and industry.
|
http://arxiv.org/abs/1708.09014v1
|
We demonstrate 140 Gbaud intensity modulated direct detection
dispersion-uncompensated links with Mach Zehnder modulator and distributed
feedback travelling-wave electro-absorption modulator over 5500 and 960 meters
of standard single mode fibre, respectively, enabled by compact packaged
ultra-high speed InP-based 2:1-Selector.
|
http://arxiv.org/abs/1811.04610v1
|
Sub-Terahertz frequencies (frequencies above 100 GHz) have the potential to satisfy the unprecedented demand on data rate on the order of hundreds of Gbps for sixth-generation (6G) wireless communications and beyond. Accurate beam tracking and rapid beam selection are increasingly important since antenna arrays with more elements generate narrower beams to compensate for additional path loss within the first meter of propagation distance at sub-THz frequencies. Realistic channel models for above 100 GHz are needed, and should include spatial consistency to model the spatial and temporal channel evolution along the user trajectory. This paper introduces recent outdoor urban microcell (UMi) propagation measurements at 142 GHz along a 39 m $\times$ 12 m rectangular route (102 m long), where each consecutive and adjacent receiver location is 3 m apart from each other. The measured power delay profiles and angular power spectrum at each receiver location are used to study spatial autocorrelation properties of various channel parameters such as shadow fading, delay spread, and angular spread along the track. Compared to the correlation distances reported in the 3GPP TR 38.901 for frequencies below 100 GHz, the measured correlation distance of shadow fading at 142 GHz (3.8 m) is much shorter than the 10-13 m as specified in 3GPP; the measured correlation distances of delay spread and angular spread at 142 GHz (both 12 m) are comparable to the 7-10 m as specified in 3GPP. This result may guide the development of a statistical spatially consistent channel model for frequencies above 100 GHz in the UMi street canyon environment.
|
https://arxiv.org/abs/2103.05496v1
|
This paper presents sub-Terahertz (THz) radio propagation measurements at 142 GHz conducted in four factories with various layouts and facilities to explore sub-THz wireless channels for smart factories in 6G and beyond. Here we study spatial and temporal channel responses at 82 transmitter-receiver (TX-RX) locations across four factories in the New York City area and over distances from 5 m to 85 m in both line-of-sight (LOS) and non-LOS (NLOS) environments. The measurements were performed with a sliding-correlation-based channel sounder with 1 GHz RF bandwidth with steerable directional horn antennas with 27 dBi gain and 8\degree~half-power beamwidth at both TX and RX, using both vertical and horizontal antenna polarizations, yielding over 75,000 directional power delay profiles. Channel measurements of two RX heights at 1.5 m (high) emulating handheld devices and at 0.5 m (low) emulating automated guided vehicles (AGVs) were conducted for automated industrial scenarios with various clutter densities. Results yield the first path loss models for indoor factory (InF) environments at 142 GHz and show the low RX height experiences a mean path loss increase of 10.7 dB and 6.0 dB when compared with the high RX height at LOS and NLOS locations, respectively. Furthermore, flat and rotatable metal plates were leveraged as passive reflecting surfaces (PRSs) in channel enhancement measurements to explore the potential power gain on sub-THz propagation channels, demonstrating a range from 0.5 to 22 dB improvement with a mean of 6.5 dB in omnidirectional channel gain as compared to when no PRSs are present.
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https://arxiv.org/abs/2302.12142v1
|
The occurrence of octupole shapes in even-mass neutron-rich Ba isotopes has been well established. However, the situation with the odd-mass Ba and odd or odd-odd La nuclei around them is far from settled. In order to shed light on these less-studied isotopes, a fast-timing experiment was performed using GRIFFIN at TRIUMF-ISAC. A wealth of excited-state lifetimes in the 100~ps to few ns range have been measured in $^{144, 145, 146}$Ba and $^{145,146}$La populated in the $\beta^-$ and $\beta^--n$ decay of $^{145,146}$Cs. The results do not allow to draw firm conclusions on the possible octupole deformation of these nuclei but suggest different spin and parity assignments than previous works. This work highlights the need for more detailed study of the odd and odd-odd isotopes in this region to properly understand their structure.
|
https://arxiv.org/abs/2109.04808v1
|
Large-language models (LLMs) such as GPT-4 caught the interest of many scientists. Recent studies suggested that these models could be useful in chemistry and materials science. To explore these possibilities, we organized a hackathon. This article chronicles the projects built as part of this hackathon. Participants employed LLMs for various applications, including predicting properties of molecules and materials, designing novel interfaces for tools, extracting knowledge from unstructured data, and developing new educational applications. The diverse topics and the fact that working prototypes could be generated in less than two days highlight that LLMs will profoundly impact the future of our fields. The rich collection of ideas and projects also indicates that the applications of LLMs are not limited to materials science and chemistry but offer potential benefits to a wide range of scientific disciplines.
|
https://arxiv.org/abs/2306.06283v4
|
This paper presents 1.4-GHz radio continuum observations of 15 very extended
radio galaxies. These sources are so large that most interferometers lose
partly their structure and total flux density. Therefore, single-dish
detections are required to fill in the central (u,v) gap of interferometric
data and obtain reliable spectral index patterns across the structures, and
thus also an integrated radio continuum spectrum. We have obtained such 1.4-GHz
maps with the 100-m Effelsberg telescope and combined them with the
corresponding maps available from the NVSS. The aggregated data allow us to
produce high-quality images, which can be used to obtain physical parameters of
the mapped sources. The combined images reveal in many cases extended low
surface-brightness cocoons.
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http://arxiv.org/abs/1604.05142v1
|
The fundamental plane of black hole activity is an empirical relationship
between the OIII/X-ray luminosity depicting the accretion power, the radio
luminosity as a probe of the instantaneous jet power and the mass of the black
hole. For the first time, we use the 1.4 GHz FIRST radio luminosities on the
optical fundamental plane, to investigate whether or not FIRST fluxes can trace
nuclear activity. We use a SDSS-FIRST cross-correlated sample of 10149 active
galaxies and analyse their positioning on the optical fundamental plane. We
focus on various reasons that can cause the discrepancy between the observed
FIRST radio fluxes and the theoretically expected core radio fluxes, and show
that that FIRST fluxes are heavily contaminated by non-nuclear, extended
components and other environmental factors. We show that the subsample of
'compact sources', which should have negligible lobe contribution,
statistically follow the fundamental plane when corrected for relativistic
beaming, while all the other sources lie above the plane. The sample of LINERs,
which should have negligible lobe and beaming contribution, also follow the
fundamental plane. A combined fit of the low-luminosity AGN and the X-ray
binaries, with the LINERs, results in the relation log L$_R$ = 0.77 log
L$_{OIII}$ + 0.69 log M. Assuming that the original fundamental plane relation
is correct, we conclude that 1.4 GHz FIRST fluxes do not trace the pure 'core'
jet and instantaneous nuclear activity in the AGN, and one needs to be careful
while using it on the fundamental plane of black hole activity.
|
http://arxiv.org/abs/1803.07286v1
|
In this Letter, we measure the full orbital architecture of the two-planet system around the nearby K0 dwarf 14 Herculis. 14 Her (HD 145675, HIP 79248) is a middle-aged ($4.6^{+3.8}_{-1.3}$ Gyr) K0 star with two eccentric giant planets identified in the literature from radial velocity (RV) variability and long-term trends. Using archival RV data from Keck/HIRES in concert with \textit{Gaia-Hipparcos} acceleration in the proper motion vector for the star, we have disentangled the mass and inclination of the b planet to ${9.1}_{-1.1}^{+1.0}$ $M_\mathrm{Jup}$ and ${32.7}_{-3.2}^{+5.3}$ degrees. Despite only partial phase coverage for the c planet's orbit, we are able to constrain its mass and orbital parameters as well to ${6.9}_{-1.0}^{+1.7}$ $M_\mathrm{Jup}$ and ${101}_{-33}^{+31}$ degrees. We find that coplanarity of the b and c orbits is strongly disfavored. Combined with the age of the system and the comparable masses of its planets, this suggests that planet-planet scattering may be responsible for the current configuration of the system.
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https://arxiv.org/abs/2111.06004v2
|
In non-interacting systems, bands from non-trivial topology emerge strictly at half-filling and exhibit either the quantum anomalous Hall or spin Hall effects. Here we show using determinantal quantum Monte Carlo and an exactly solvable strongly interacting model that these topological states now shift to quarter filling. A topological Mott insulator is the underlying cause. The peak in the spin susceptibility is consistent with a possible ferromagnetic state at $T=0$. The onset of such magnetism would convert the quantum spin Hall to a quantum anomalous Hall effect. While such a symmetry-broken phase typically is accompanied by a gap, we find that the interaction strength must exceed a critical value for this to occur. Hence, we predict that topology can obtain in a gapless phase but only in the presence of interactions in dispersive bands. These results explain the recent quarter-filled quantum anomalous Hall effects seen in moire systems.
|
https://arxiv.org/abs/2210.11486v5
|
The Single Aperture Large Telescope for Universe Studies (SALTUS) is a deployable space telescope designed to provide the astrophysics community with an extremely large far-infrared (far-IR) space observatory to explore our cosmic origins. The SALTUS observatory can observe thousands of faint astrophysical targets, including the first galaxies, protoplanetary disks in various evolutionary states, and a wide variety of solar system objects. The SALTUS design architecture utilizes radiatively cooled, 14-m diameter unobscured aperture, and cryogenic instruments to enable both high spectral and spatial resolution at unprecedented sensitivity over a wavelength range largely unavailable to any existing ground or space observatories. The unique SALTUS optical design, utilizing a large inflatable off-axis primary mirror, provides superb sensitivity, angular resolution, and imaging performance at far-IR wavelengths over a wide +/-0.02 x 0.02 degree Field of View. SALTUS design, with its highly compact form factor, allows it to be readily stowed in available launch fairings and subsequently deployed in orbit.
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https://arxiv.org/abs/2405.19584v1
|
The AM-DeepSeek-R1-Distilled is a large-scale dataset with thinking traces for general reasoning tasks, composed of high-quality and challenging reasoning problems. These problems are collected from a multitude of open-source datasets, subjected to semantic deduplication and meticulous cleaning to eliminate test set contamination. All responses within the dataset are distilled from reasoning models (predominantly DeepSeek-R1) and have undergone rigorous verification procedures. Mathematical problems are validated by checking against reference answers, code problems are verified using test cases, and other tasks are evaluated with the aid of a reward model. The AM-Distill-Qwen-32B model, which was trained through only simple Supervised Fine-Tuning (SFT) using this batch of data, outperformed the DeepSeek-R1-Distill-Qwen-32B model on four benchmarks: AIME2024, MATH-500, GPQA-Diamond, and LiveCodeBench. Additionally, the AM-Distill-Qwen-72B model surpassed the DeepSeek-R1-Distill-Llama-70B model on all benchmarks as well. We are releasing these 1.4 million problems and their corresponding responses to the research community with the objective of fostering the development of powerful reasoning-oriented Large Language Models (LLMs). The dataset was published in \href{https://huggingface.co/datasets/a-m-team/AM-DeepSeek-R1-Distilled-1.4M}{https://huggingface.co/datasets/a-m-team/AM-DeepSeek-R1-Distilled-1.4M}.
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https://arxiv.org/abs/2503.19633v1
|
Free-space super-strong terahertz (THz) electromagnetic fields offer
multifaceted capabilities for reaching extreme nonlinear THz optics,
accelerating and manipulating charged particles, and realizing other
fascinating applications. However, the lack of powerful solid-state THz sources
with single pulse energy >1 mJ is impeding the proliferation of extreme THz
applications. The fundamental challenge lies in hard to achieve high efficiency
due to high intensity pumping caused crystal damage, linear absorption and
nonlinear distortion induced short effective interaction length, and so on.
Here, through cryogenically cooling the crystals, delicately tailoring the pump
laser spectra, chirping the pump pulses, and magnifying the laser energies, we
first successfully realized the generation of 1.4-mJ THz pulses lithium
niobates under the excitation of 214-mJ femtosecond laser pulses via tilted
pulse front technique. The 800 nm-to-THz energy conversion efficiency reached
0.7%, and a free-space THz peak electric and magnetic fields reached 6.3 MV/cm
and 2.1 Tesla. Our numerical simulations based on a frequencydomain
second-order nonlinear wave equation under slowly varying envelope
approximation reproduced the experimental optimization processes. To show the
capability of this super-strong THz source, nonlinear absorption due to
field-induced intervalley scattering effect in high conductive silicon induced
by strong THz electric field was demonstrated. Such a high energy THz source
with a relatively low peak frequency is very appropriate not only for electron
acceleration towards table-top X-ray sources but also for extreme THz science
and nonlinear applications.
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http://arxiv.org/abs/2007.09322v1
|
Ions in Hall effect thrusters are often characterized by a low collisionality. In the presence of acceleration fields and azimuthal electric field waves, this results in strong deviations from thermodynamic equilibrium, introducing kinetic effects. This work investigates the application of the 14-moment maximum-entropy model to this problem. This method consists in a set of 14 PDEs for the density, momentum, pressure tensor components, heat flux vector and fourth-order moment associated to the particle velocity distribution function. The model is applied to the study of collisionless ion dynamics in a Hall thruster-like configuration, and its accuracy is assessed against different models, including the Vlasov kinetic equation. Three test cases are considered: a purely axial acceleration problem, the problem of ion-wave trapping and finally the evolution of ions in the axial-azimuthal plane. Most of this work considers ions only, and the coupling with electrons is removed by prescribing reasonable values of the electric field. This allows us to obtain a direct comparison among different ion models. However, the possibility to run self-consistent plasma simulations is also briefly discussed, considering quasi-neutral or multi-fluid models. The maximum-entropy system appears to be a robust and accurate option for the considered test cases. The accuracy is improved over the simpler pressureless gas model (cold ions) and the Euler equations for gas dynamics, while the computational cost shows to remain much lower than direct kinetic simulations.
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https://arxiv.org/abs/2202.04159v3
|
The abundance ratio of $^{14}$N$/^{15}$N is, in principle, a powerful tool for tracing stellar nucleosynthesis. This work aims to measure and analyze ($^{14}$N/$^{15}$N)$\times$($^{13}$C/$^{12}$C) and $^{14}$N$/^{15}$N abundance ratios in massive star-forming regions across a range of galactocentric distances to provide constraints on galactic chemical evolution (GCE) models. We present H$^{13}$CN and HC$^{15}$N J=2-1 results toward 51massive star-forming regions obtained with the Institut de Radioastronomie Millim\'etrique (IRAM) 30 meter telescope.\ We used these results to derive ($^{14}$N/$^{15}$N)$\times$($^{13}$C/$^{12}$C) abundance ratios as well as $^{14}$N$/^{15}$N ratios using the double isotope method. We find an overall decreasing trend in the ($^{14}$N/$^{15}$N)$\times$($^{13}$C/$^{12}$C) abundance ratio and an increasing trend in the $^{14}$N$/^{15}$N ratio with increasing galactocentric distance ($D_{\rm GC}$), which provides a good constraint for the GCE model based on high signal to noise ratio measurements. While the predicted ($^{14}$N/$^{15}$N)$\times$($^{13}$C/$^{12}$C) ratios between 6 and 12 kpc determined using current GCE models are consistent with our observational results, the ratios from models for $D_{\rm GC}$ less than 6 kpc are significantly higher than the observational results, which indicates GCE models for $^{14}$N/$^{15}$N and/or $^{13}$C/$^{12}$C ratios need to be updated for at least this range.
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https://arxiv.org/abs/2503.02520v1
|
Here we present an analysis of 14 transit light curves of the hot Jupiter HAT-P-54 b. Thirteen of our datasets were obtained with the 6-inch MicroObservatory telescope, Cecilia, and one was measured with the 61-inch Kuiper Telescope. We used the EXOplanet Transit Interpretation Code (EXOTIC) to reduce 49 datasets in order to update the planet's ephemeris to a mid-transit time of 2460216.95257 +/- 0.00022 BJD_TBD and an updated orbital period of 3.79985363 +/- 0.00000037 days. These results improve the mid-transit uncertainty by 70.27% from the most recent ephemeris update. The updated mid-transit time can help to ensure the efficient use of expensive, large ground- and space-based telescope missions in the future. This result demonstrates that amateur astronomers and citizen scientists can provide meaningful, cost-efficient, crowd-sourcing observations using ground-based telescopes to further refine current mid-transit times and orbital periods.
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https://arxiv.org/abs/2406.18487v1
|
The nitrogen-vacancy (NV) centers (NCVSi) - in 4H silicon carbide (SiC) constitute an ensemble of spin S = 1 solid state qubits interacting with the surrounding 14N and 29Si nuclei. As quantum applications based on a polarization transfer from the electron spin to the nuclei require the knowledge of the electron-nuclear interaction parameters, we have used high-frequency (94 GHz) electron-nuclear double resonance spectroscopy combined with first-principles density functional theory to investigate the hyperfine and nuclear quadrupole interactions of the basal and axial NV centers. We observed that the four inequivalent NV configurations (hk, kh, hh, and kk) exhibit different electron-nuclear interaction parameters, suggesting that each NV center may act as a separate optically addressable qubit. Finally, we rationalized the observed differences in terms of distinctions in the local atomic structures of the NV configurations. Thus, our results provide the basic knowledge for an extension of quantum protocols involving the 14N nuclear spin.
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https://arxiv.org/abs/2404.06933v1
|
In this paper, 14-velocity and 18-velocity multiple-relaxation-time (MRT)
lattice Boltzmann (LB) models are proposed for three-dimensional incompressible
flows. These two models are constructed based on the incompressible LBGK model
proposed by He et al. (Chin. Phys., 2004, 13: 40-46) and the MRT LB model
proposed by d'Humi\`{e}res et al. (Philos. Trans. R. Soc., A, 2002, 360:
437-451), which have advantages in the computational efficiency and stability,
respectively. Through the Chapman-Enskog analysis, the models can recover to
three-dimensional incompressible Navier-Stokes equations in the low Mach number
limit. To verify the present models, the steady Poiseuille flow, unsteady
pulsatile flow and lid-driven cavity flow in three dimensions are simulated.
The simulation results agree well with the analytical solutions or the existing
numerical results. Moreover, it is found that the present models show higher
accuracy than d'Humi\`{e}res et al. model and better stability than He et al.
model.
|
http://arxiv.org/abs/1503.03337v1
|
In today's connected society, many people rely on mHealth and self-tracking (ST) technology to help them adopt healthier habits with a focus on breaking their sedentary lifestyle and staying fit. However, there is scarce evidence of such technological interventions' effectiveness, and there are no standardized methods to evaluate their impact on people's physical activity (PA) and health. This work aims to help ST practitioners and researchers by empowering them with systematic guidelines and a framework for designing and evaluating technological interventions to facilitate health behavior change (HBC) and user engagement (UE), focusing on increasing PA and decreasing sedentariness. To this end, we conduct a literature review of 129 papers between 2008 and 2022, which identifies the core ST HCI design methods and their efficacy, as well as the most comprehensive list to date of UE evaluation metrics for ST. Based on the review's findings, we propose PAST SELF, a framework to guide the design and evaluation of ST technology that has potential applications in industrial and scientific settings. Finally, to facilitate researchers and practitioners, we complement this paper with an open corpus and an online, adaptive exploration tool for the PAST SELF data.
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https://arxiv.org/abs/2104.11483v3
|
We present a homogeneously-selected sample of 15779 candidate binary systems with main sequence primary stars and orbital periods shorter than 5 days. The targets were selected from TESS full-frame image lightcurves on the basis of their tidally-induced ellipsoidal modulation. Spectroscopic follow-up suggests a sample purity of $83 \pm 13$ per cent. Injection-recovery tests allow us to estimate our overall completeness as $28 \pm 3$ per cent with $P_\mathrm{orb} < 3$ days and to quantify our selection effects. We estimate that $39 \pm 4$ per cent of our sample are contact binary systems, and we disentangle the period distributions of the contact and detached binaries. We derive the orbital period distribution of the main sequence binary population at short orbital periods, finding a distribution continuous with the log-normal distribution previously found for solar-type stars at longer periods, but with a significant steepening at $P_\mathrm{orb} \lesssim 3$ days, and a pile-up of contact binaries at $P_\mathrm{orb} \approx 0.4$ days. Companions in the period range 1--5 days are found to be an order of magnitude more frequent around stars hotter than $\approx 6250 K$ (the Kraft break) when compared to cooler stars, suggesting that magnetic braking plays an important role in shaping the temperature and period distributions. We detect resolved tertiary companions to $9.0 \pm 0.2$ per cent of our binaries with a median separation of 3200 AU. The frequency of tertiary companions rises to $29 \pm 5$ per cent among the systems with the shortest ellipsoidal periods. This large binary sample with quantified selection effects will be a powerful resource for future studies of detached and contact binary systems with $P_\mathrm{orb} < 5$ days.
|
https://arxiv.org/abs/2211.06194v2
|
This article is an extended version of the article published by EDP Sciences at the occasion of the 150 years of the ``Soci\'et\'e Fran\c{c}aise de Physique'' (in French)
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https://arxiv.org/abs/2311.15042v1
|
Using new annual data of 16 developed countries across bond, equity, and housing markets, I study the return predictability using the payout-price ratios, i.e., coupon price, dividend price, and rent price. None of the 48 country-asset combinations shows consistent in-sample and out-of-sample performance with positive utility gain for the mean-variance investor. Only 3 (4/2) countries show positive economic gains in their equity (housing/bond) markets. The return predictability for the representative agents' risky asset portfolios and wealth portfolios is even weaker, suggesting that timing the investment return of a country using payout-price ratios will not make the investors better off. The predictive regressions based on the VAR analysis by Cochrane (2008, 2011) suggest that 14 (5) countries have predictable payout growth in the equity (housing) markets, ex., the dividend price predicts the dividend growth in the US. The VAR simulation using data from all the countries does not reject the null that the dividend growth is predictable. This paper presents firm evidence against the return predictability based on payout ratios.
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https://arxiv.org/abs/2209.00121v1
|
This book, which is in Spanish, provides detailed descriptions, including over 550 mathematical formulas, for over 150 trading strategies across a host of asset classes (and trading styles). This includes stocks, options, fixed income, futures, ETFs, indexes, commodities, foreign exchange, convertibles, structured assets, volatility (as an asset class), real estate, distressed assets, cash, cryptocurrencies, miscellany (such as weather, energy, inflation), global macro, infrastructure, and tax arbitrage. Some strategies are based on machine learning algorithms (such as artificial neural networks, Bayes, k-nearest neighbors). We also give: source code for illustrating out-of-sample backtesting with explanatory notes; around 2,000 bibliographic references; and over 900 glossary, acronym and math definitions. The presentation is intended to be descriptive and pedagogical. ----- Este libro proporciona descripciones detalladas, que incluyen m\'as de 550 f\'ormulas matem\'aticas, para m\'as de 150 estrategias de trading para una gran cantidad de clases de activos y estilos de trading. Esto incluye acciones, opciones, bonos (renta fija), futuros, ETFs, \'indices, commodities, divisas, bonos convertibles, activos estructurados, volatilidad (como clase de activos), bienes inmuebles, activos en distress, efectivo, criptomonedas, miscel\'aneos (como clima, energ\'ia, inflaci\'on), macro global, infraestructura y arbitraje impositivo. Algunas estrategias se basan en algoritmos de aprendizaje autom\'atico (como redes neuronales artificiales, Bayes, k vecinos m\'as cercanos). El libro tambi\'en incluye c\'odigo para backtesting fuera de la muestra con notas explicativas; cerca de 2,000 referencias bibliogr\'aficas; m\'as de 900 t\'erminos que comprenden el glosario, acr\'onimos y definiciones matem\'aticas. La presentaci\'on pretende ser descriptiva y pedag\'ogica.
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https://arxiv.org/abs/1912.04492v1
|
We have detected four flares from UV Ceti at 154 MHz using the Murchison
Widefield Array. The flares have flux densities between 10--65 mJy --- a factor
of 100 fainter than most flares in the literature at these frequencies --- and
are only detected in polarization. The circular polarized fractions are limited
to $>27$% at 3$\sigma$ confidence and two of the flares exhibit polarity
reversal. We suggest that these flares occur periodically on a time scale
consistent with the rotational period of UV Ceti. During the brightest observed
flare, we also detect significant linear polarization with polarization
fraction $>18$%. Averaging the data in 6-minute, 10 MHz frequency bins we find
that the flux density of these flares does not vary over the 30 MHz bandwidth
of the Murchison Widefield Array, however we cannot rule out finer
time-frequency structure. Using the measured flux densities for the flares, we
estimate brightness temperatures between $(10^{13}-10^{14})\,$K, indicative of
a coherent emission mechanism. The brightness temperature and polarization
characteristics point to the electron cyclotron maser mechanism. We also
calculate the flare rates given our four observed flares and compare them to
flare rates for the set of M dwarf stars with known 100--200 MHz flares. Our
measurement is the first for flares with intensities $<100$ mJy at 100-200 MHz.
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http://arxiv.org/abs/1702.03030v1
|
BACKGROUND: 155Tb represents a potentially useful radionuclide for diagnostic medical applications, but its production remains a challenging problem. A recent experimental campaign, conducted with low-energy proton beams impinging on a 155Gd target with 91.9% enrichment, demonstrated a significant co-production of 156gTb, a contaminant of great concern since its half-life is comparable to that of 155Tb and its high-energy gamma emissions severely impact on the dose released and on the quality of the SPECT images. Herein, the isotopic purity of the enriched 155Gd target necessary to minimize the co-production of contaminant radioisotopes, in particular 156gTb, was explored using various computational simulations. RESULTS: Starting from the recent data obtained with the 155Gd-enriched target, the co-production of other Tb radioisotopes besides 155Tb has been evaluated using the TALYS code. It was found that 156Gd, with an isotopic content of 5.87%, was the principal contributor to the co-production of 156gTb. The analysis also demonstrated that the maximum amount of 156Gd admissible for 155Tb production with a radionuclidic purity higher than 99% was 1%. A less stringent condition was obtained through computational dosimetry analysis, suggesting that a 2% content of 156Gd in the target can be tolerated to limit the dose increase to the patient below the 10% limit. Moreover, it has been demonstrated that the imaging properties of the produced 155Tb are not severely affected by this level of impurity in the target. CONCLUSIONS: 155Tb can be produced with a quality suitable for medical applications using low-energy proton beams and 155Gd-enriched targets if the 156Gd impurity content does not exceed 2%. Under these conditions, the dose increase due to the presence of contaminant radioisotopes remains below the 10% limit and good quality images, comparable to those of 111In, are guaranteed.
|
https://arxiv.org/abs/2309.06250v1
|
We present 1.58-bit FLUX, the first successful approach to quantizing the state-of-the-art text-to-image generation model, FLUX.1-dev, using 1.58-bit weights (i.e., values in {-1, 0, +1}) while maintaining comparable performance for generating 1024 x 1024 images. Notably, our quantization method operates without access to image data, relying solely on self-supervision from the FLUX.1-dev model. Additionally, we develop a custom kernel optimized for 1.58-bit operations, achieving a 7.7x reduction in model storage, a 5.1x reduction in inference memory, and improved inference latency. Extensive evaluations on the GenEval and T2I Compbench benchmarks demonstrate the effectiveness of 1.58-bit FLUX in maintaining generation quality while significantly enhancing computational efficiency.
|
https://arxiv.org/abs/2412.18653v1
|
{ The ground-state to ground-state electron-capture $Q$ value of $^{159}$Dy ($3/2^-$) has been measured directly utilizing the double Penning trap mass spectrometer JYFLTRAP. A value of 364.73(19)~keV was obtained from a measurement of the cyclotron frequency ratio of the decay parent $^{159}$Dy and the decay daughter $^{159}$Tb ions using the novel phase-imaging ion-cyclotron resonance technique. The $Q$ values for allowed Gamow-Teller transition to $5/2^-$ and the third-forbidden unique transition to $11/2^+$ state with excitation energies of 363.5449(14)~keV and 362.050(40)~keV in $^{159}$Tb were determined to be 1.18(19) keV and 2.68(19) keV, respectively. The high-precision $Q$ value of transition $3/2^-\to 5/2^-$ from this work, revealing itself as the lowest electron-capture $Q$ value, is utilized to unambiguously characterise all the possible lines that are present in its electron capture spectrum. { We performed atomic many-body calculations for both transitions to determine electron-capture probabilities from various atomic orbitals, and found an order of magnitude enhancement in the event rates near the end-point of energy spectrum in the transition to the $5/2^-$ nuclear excited state, which can become very interesting once the experimental challenges of identifying decays into excited states are overcome. The transition to the $11/2^+$ state is strongly suppressed and found unsuitable for measuring the neutrino mass. These results show that the electron capture in the $^{159}$Dy atom, going to the $5/2^-$ state of the $^{159}$Tb nucleus, %\textcolor{red} {is a new candidate which may open the way to determine the electron-neutrino mass in the sub-eV region by studying EC. Further experimental feasibility studies, including coincidence measurements with realistic detectors, will be of great interest.} }
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https://arxiv.org/abs/2106.06626v2
|
Quasi-one-dimensional magnets can host an ordered longitudinal spin-density wave state (LSDW) in magnetic field at low temperature, when longitudinal correlations are strengthened by Ising anisotropies. In the S = 1/2 Heisenberg antiferromagnet YbAlO3 this happens via Ising-like interchain interactions. Here, we report the first experimental observation of magnetization plateaux at 1/5 and 1/3 of the saturation value via thermal transport and magnetostriction measurements in YbAlO3. We present a phenomenological theory of the plateau states that describes them as islands of commensurability within an otherwise incommensurate LSDW phase and explains their relative positions within the LSDW phase and their relative extent in a magnetic field. Notably, the plateaux are stabilised by ferromagnetic interchain interactions in YbAlO3 and consistently are absent in other quasi-1D magnets such as BaCo2V2O8 with antiferromagnetic interchain interactions. We also report a small, step-like increase of the magnetostriction coefficient, indicating a weak phase transition of unknown origin in the high-field phase just below the saturation.
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https://arxiv.org/abs/2412.21144v2
|
This study is an attempt to build a contemporary linguistic corpus for Arabic
language. The corpus produced, is a text corpus includes more than five million
newspaper articles. It contains over a billion and a half words in total, out
of which, there is about three million unique words. The data were collected
from newspaper articles in ten major news sources from eight Arabic countries,
over a period of fourteen years. The corpus was encoded with two types of
encoding, namely: UTF-8, and Windows CP-1256. Also it was marked with two
mark-up languages, namely: SGML, and XML.
|
http://arxiv.org/abs/1611.04033v1
|
Neuromorphic vision processor is an electronic implementation of vision
algorithm processor on semiconductor. To image the world, a low-power CMOS
image sensor array is required in the vision processor. The image sensor array
is typically formed through photo diodes and analog to digital converter (ADC).
To achieve low power acquisition, a low-power mid-resolution ADC is necessary.
In this paper, a 1.8V, 8-bit, 166MS/s pipelined ADC was proposed in a 0.18 um
CMOS technology. The ADC used operational amplifier sharing architecture to
reduce power consumption and achieved maximum DNL of 0.24 LSB, maximum INL of
0.35 LSB, at a power consumption of 38.9mW. When input frequency is 10.4MHz, it
achieved an SNDR 45.9dB, SFDR 50dB, and an ENOB of 7.33 bit.
|
http://arxiv.org/abs/1701.08877v2
|
In order to facilitate IR absorption measurements of mass-selected ions
isolated in cryogenic matrices, we have upgraded an ion beam deposition
apparatus encompassing a Bruker IFS66v/S FTIR spectrometer. A synthetic diamond
beam splitter without compensator plate and UHV diamond viewports were
installed. We have also modified the IR detector chamber to allow measurements
with 5 different detectors. As a result we can now obtain FT absorption spectra
from 12000 cm$^{-1}$ to 15 cm$^{-1}$ with the same sample held under ultrahigh
vacuum conditions, simply by switching between appropriate IR detectors. We
demonstrate performance of the upgraded FTIR spectrometer by presenting
measurements of matrix isolated fullerene ions and an adhesive tape.
|
http://arxiv.org/abs/1610.06698v1
|
We have established an iterative scheme to calculate with 15-digit accuracy
the numerical values of Ambartsumian-Chandrasekhar's H-functions for
anisotropic scattering characterized by the four-term phase function: the
method incorporates some advantageous features of the iterative procedure of
Kawabata (2015) and the double-exponential integration formula~(DE-formula) of
Takahashi and Mori (1974), which proved highly effective in Kawabata (2016).
Actual calculations of the H-functions have been carried out employing 27
selected cases of the phase function, 56 values of the single scattering albedo
$\varpi_0$, and 36 values of an angular variable $\mu(=\cos \theta)$, with
$\theta$ being the zenith angle specifying the direction of incidence and/or
emergence of radiation.
Partial results obtained for conservative isotropic scattering, Rayleigh
scattering, and anisotropic scattering due to a full four-term phase function
are presented. As a sample application of the isotropic scattering H-function,
an attempt is made in Appendix to simulate by iteratively solving the
Ambartsumian equation the values of the plane and spherical albedos of a
semi-infinite, homogeneous atmosphere calculated by Rogovtsov and Borovik
(2016), who employed their analytical representations for these quantities and
the single-term and two-term Henyey-Greenstein phase functions of appreciably
high degrees of anisotropy, to find that our results are in satisfactory
agreement with theirs.
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http://arxiv.org/abs/1712.04790v1
|
This work shows that it is possible to calculate numerical values of the
Chandrasekhar $H$-function for isotropic scattering at least with 15-digit
accuracy by making use of the double exponential formula (DE-formula) of
Takahashi and Mori (Publ. RIMS, Kyoto Univ. Vol. 9, 721, 1974) instead of the
Gauss-Legendre quadrature employed in the numerical scheme of Kawabata and
Limaye (Astrophys. Space Sci. Vol. 332, 365, 2011) and simultaneously taking a
precautionary measure to minimize the effects due to loss of significant digits
particularly in the cases of near-conservative scattering and/or errors
involved in returned values of library functions supplied by compilers in use.
The results of our calculations are presented for 18 selected values of single
scattering albedo $\varpi_0$ and 22 values of an angular variable $\mu$, the
cosine of zenith angle $\theta$ specifying the direction of radiation incident
on or emergent from semi-infinite media.
|
http://arxiv.org/abs/1611.10197v1
|
Aims. We here demonstrate how the recently developed Lightweaver framework makes non-LTE (NLTE) spectral synthesis feasible on a new 3D ab-initio magnetohydrodynamic (MHD) filament/prominence simulation, in a post-processing step. Methods. We clarify the need to introduce filament/prominent-specific Lightweaver boundary conditions that accurately model incident chromospheric radiation, and include a self-consistent and smoothly varying limb darkening function. Results. Progressing from isothermal/isobaric models to the self-consistently generated stratifications within a fully 3D MHD filament/prominence simulation, we find excellent agreement between our 1.5D non local thermodynamic equilibrium Lightweaver synthesis and a popular Hydrogen H{\alpha} proxy. We compute additional lines including Ca~\textsc{ii} 8542 alongside the more optically-thick Ca~\textsc{ii} H&K & Mg~\textsc{ii} h&k lines, for which no comparable proxy exists, and explore their formation properties within filament/prominence atmospheres. Conclusions. The versatility of the Lightweaver framework is demonstrated with this extension to 1.5D filament/prominence models, where each vertical column of the instantaneous 3D MHD state is spectrally analysed separately, without accounting for (important) multi-dimensional radiative effects. The general agreement found in the line core contrast of both observations and the Lightweaver-synthesised simulation further validates the current generation of solar filaments/prominences models constructed numerically with MPI-AMRVAC.
|
https://arxiv.org/abs/2211.14869v1
|
The transfer of population between two intersecting quantum states is the most fundamental dynamical event that governs a broad variety of processes in physics, chemistry, biology and material science. Whereas any two-state description implies that population leaving one state instantaneously appears in the other state, we show that coupling to additional states, present in all real-world systems, can cause a measurable delay in population transfer. Using attosecond spectroscopy supported by advanced quantum-chemical calculations, we measure a delay of 1.46$\pm$0.41 fs at a charge-transfer state crossing in CF$_3$I$^+$, where an electron hole moves from the fluorine atoms to iodine. Our measurements also fully resolve the other fundamental quantum-dynamical processes involved in the charge-transfer reaction: a vibrational rearrangement time of 9.38$\pm$0.21 fs (during which the vibrational wave packet travels to the state crossing) and a population-transfer time of 2.3-2.4 fs. Our experimental results and theoretical simulations show that delays in population transfer readily appear in otherwise-adiabatic reactions and are typically on the order of 1 fs for intersecting molecular valence states. These results have implications for many research areas, such as atomic and molecular physics, charge transfer or light harvesting.
|
https://arxiv.org/abs/2408.17402v1
|
We present a sub-arcsec resolution radio imaging survey of a sample of 76
low-luminosity active galactic nuclei (LLAGN) that were previously not detected
with the Very Large Array at 15 GHz. Compact, parsec-scale radio emission has
been detected above a flux density of 40 $\mu$Jy in 60% (45 of 76) of the LLAGN
sample. We detect 20 out of 31 (64%) low-ionization nuclear emission-line
region (LINER) nuclei, ten out of 14 (71%) low-luminosity Seyfert galaxies, and
15 out of 31 (48%) transition objects. We use this sample to explore
correlations between different emission lines and the radio luminosity. We also
populate the X-ray and the optical fundamental plane of black hole activity and
further refine its parameters. We obtain a fundamental plane relation of log
L$_\textrm{R}$ = $0.48\,(\pm0.04$) log L$_\textrm{X}$ + $0.79\,(\pm0.03$) log
$\textrm{M}$ and an optical fundamental plane relation of log L$_\textrm{R}$ =
$0.63\,(\pm 0.05)$ log L$_{[\rm O~III]}$ + $0.67\,(\pm 0.03)$ log $\textrm{M}$
after including all the LLAGN detected at high resolution at 15 GHz, and the
best-studied hard-state X-ray binaries (luminosities are given in erg s$^{-1}$
while the masses are in units of solar mass). Finally, we find conclusive
evidence that the nuclear 15 GHz radio luminosity function (RLF) of all the
detected Palomar Sample LLAGN has a turnover at the low-luminosity end, and is
best-fitted with a broken power law. The break in the power law occurs at a
critical mass accretion rate of 1.2$\times$10$^{-3}$ M$_{\odot}$/yr, which
translates to an Eddington ratio of $\rm \dot m_{Edd} \sim 5.1 \times 10^{-5}$,
assuming a black hole mass of 10$^9 M_{\odot}$. The local group stands closer
to the extrapolation of the higher-luminosity sources, and the classical
Seyferts agree with the nuclear RLF of the LLAGN in the local universe.
|
http://arxiv.org/abs/1805.06696v2
|
Pose tracking is an important problem that requires identifying unique human pose-instances and matching them temporally across different frames of a video. However, existing pose tracking methods are unable to accurately model temporal relationships and require significant computation, often computing the tracks offline. We present an efficient Multi-person Pose Tracking method, KeyTrack, that only relies on keypoint information without using any RGB or optical flow information to track human keypoints in real-time. Keypoints are tracked using our Pose Entailment method, in which, first, a pair of pose estimates is sampled from different frames in a video and tokenized. Then, a Transformer-based network makes a binary classification as to whether one pose temporally follows another. Furthermore, we improve our top-down pose estimation method with a novel, parameter-free, keypoint refinement technique that improves the keypoint estimates used during the Pose Entailment step. We achieve state-of-the-art results on the PoseTrack'17 and the PoseTrack'18 benchmarks while using only a fraction of the computation required by most other methods for computing the tracking information.
|
https://arxiv.org/abs/1912.02323v2
|
The advent of artificial intelligence (AI) has enabled a comprehensive exploration of materials for various applications. However, AI models often prioritize frequently encountered materials in the scientific literature, limiting the selection of suitable candidates based on inherent physical and chemical properties. To address this imbalance, we have generated a dataset of 1,494,017 natural language-material paragraphs based on combined OQMD, Materials Project, JARVIS, COD and AFLOW2 databases, which are dominated by ab initio calculations and tend to be much more evenly distributed on the periodic table. The generated text narratives were then polled and scored by both human experts and ChatGPT-4, based on three rubrics: technical accuracy, language and structure, and relevance and depth of content, showing similar scores but with human-scored depth of content being the most lagging. The merger of multi-modality data sources and large language model (LLM) holds immense potential for AI frameworks to help the exploration and discovery of solid-state materials for specific applications.
|
https://arxiv.org/abs/2308.13687v1
|
Currently, image-text-driven multi-modal deep learning models have demonstrated their outstanding potential in many fields. In practice, tasks centered around facial images have broad application prospects. This paper presents \textbf{FaceCaption-15M}, a large-scale, diverse, and high-quality dataset of facial images accompanied by their natural language descriptions (facial image-to-text). This dataset aims to facilitate a study on face-centered tasks. FaceCaption-15M comprises over 15 million pairs of facial images and their corresponding natural language descriptions of facial features, making it the largest facial image-caption dataset to date. We conducted a comprehensive analysis of image quality, text naturalness, text complexity, and text-image relevance to demonstrate the superiority of FaceCaption-15M. To validate the effectiveness of FaceCaption-15M, we first trained a facial language-image pre-training model (FLIP, similar to CLIP) to align facial image with its corresponding captions in feature space. Subsequently, using both image and text encoders and fine-tuning only the linear layer, our FLIP-based models achieved state-of-the-art results on two challenging face-centered tasks. The purpose is to promote research in the field of face-related tasks through the availability of the proposed FaceCaption-15M dataset. All data, codes, and models are publicly available. https://huggingface.co/datasets/OpenFace-CQUPT/FaceCaption-15M
|
https://arxiv.org/abs/2407.08515v2
|
We present an InP-based epitaxially regrown photonic crystal surface emitting
laser diode, lasing in quasi- CW conditions at 1523nm.
|
http://arxiv.org/abs/2010.09306v1
|
Nitrogen is one of the most abundant elements in the Universe and its 14N/15N
isotopic ratio has the potential to provide information about the initial
environment in which our Sun formed. Recent findings suggest that the Solar
System may have formed in a massive cluster since the presence of short-lived
radioisotopes in meteorites can only be explained by the influence of a
supernova. The aim of this project is to determine the 14N/15N ratio towards a
sample of cold, massive dense cores at the initial stages in their evolution.
We have observed the J=1-0 transitions of HCN, H13CN, HC15N, HN13C and H15NC
toward a sample of 22 cores in 4 Infrared-Dark Clouds (IRDCs). IRDCs are
believed to be the precursors of high-mass stars and star clusters. Assuming
LTE and a temperature of 15K, the column densities of HCN, H13CN, HC15N, HN13C
and H15NC are calculated and their 14N/15N ratio is determined for each core.
The 14N/15N ratio measured in our sample of IRDC cores range between ~70 and
>763 in HCN and between ~161 and ~541 in HNC. They are consistent with the
terrestrial atmosphere (TA) and protosolar nebula (PSN) values, and with the
ratios measured in low-mass pre-stellar cores. However, the 14N/15N ratios
measured in cores C1, C3, F1, F2 and G2 do not agree with the results from
similar studies toward the same massive cores using nitrogen bearing molecules
with nitrile functional group (-CN) and nitrogen hydrides (-NH) although the
ratio spread covers a similar range. Amongst the 4 IRDCs we measured relatively
low 14N/15N ratios towards IRDC G which are comparable to those measured in
small cosmomaterials and protoplanetary disks. The low average gas density of
this cloud suggests that the gas density, rather than the gas temperature, may
be the dominant parameter influencing the initial nitrogen isotopic composition
in young PSN.
|
http://arxiv.org/abs/1705.04082v1
|
Brown dwarfs serve as ideal laboratories for studying the atmospheres of giant exoplanets on wide orbits as the governing physical and chemical processes in them are nearly identical. Understanding the formation of gas giant planets is challenging, often involving the endeavour to link atmospheric abundance ratios, such as the carbon-to-oxygen (C/O) ratio, to formation scenarios. However, the complexity of planet formation requires additional tracers, as the unambiguous interpretation of the measured C/O ratio is fraught with complexity. Isotope ratios, such as deuterium-to-hydrogen and 14N/15N, offer a promising avenue to gain further insight into this formation process, mirroring their utility within the solar system. For exoplanets only a handful of constraints on 12C/13C exist, pointing to the accretion of 13C-rich ice from beyond the disks' CO iceline. Here we report on the mid-infrared detection of the 14NH3 and 15NH3 isotopologues in the atmosphere of a cool brown dwarf with an effective temperature of 380 K in a spectrum taken with the Mid-InfraRed Instrument of the James Webb Space Telescope. As expected, our results reveal a 14N/15N value consistent with star-like formation by gravitational collapse, demonstrating that this ratio can be accurately constrained. Since young stars and their planets should be more strongly enriched in the 15N isotope, we expect that 15NH3 will be detectable in a number of cold, wide-separation exoplanets.
|
https://arxiv.org/abs/2311.08054v1
|
We explain a classical construction of a del Pezzo surface of degree d = 4 or
5 as a smooth order two congruence of lines in 3-space whose focal surface is a
quartic surface $X_{20-d}$ with 20-d ordinary double points. We also show that
$X_{15}$ can be realized as a hyperplane section of the
Castelnuovo-Richmond-Igusa quartic hypersurface. This leads to the proof of
rationality of the moduli space of 15-nodal quartic surfaces. We discuss some
other birational models of $X_{15}$: quartic symmetroids, 5-nodal quartic
surfaces, 10-nodal sextic surfaces in $P^4$ and nonsingular surfaces of degree
10 in $P^6$. Finally we study some birational involutions of a 15-nodal quartic
surface which, as it is shown in Part 2 of the paper jointly with I. Shimada,
belong to a finite set of generators of the group of birational automorphisms
of a general 15-nodal quartic surface.
|
http://arxiv.org/abs/1906.12295v2
|
We describe a set of generators and defining relations for the group of
birational automorphisms of a general 15-nodal quartic surface in the complex
projective 3-dimensional space.
|
http://arxiv.org/abs/1908.05390v3
|
This paper presents a compute-efficient approach to pre-training a Language Model-the "1.5-Pints"-in only 9 days, while outperforming state-of-the-art models as an instruction-following assistant.Based on MT-Bench (a benchmark that emulates human judgments), 1.5-Pints outperforms Apple's OpenELM and Microsoft's Phi.This is achieved by a carefully curated pre-training dataset of 57 billion tokens, using a mix of automated workflows and manual human review. The selection of the dataset prioritizes content that is considered expository and "textbook-like" to aid the model in reasoning and logical deduction, culminating in its overall ability as a strong and versatile AI model. In terms of the model architecture, we employed a modified Mistral tokenizer, alongside a Llama-2 architecture for wider compatibility. For training, we adopted the methodologies used by StableLM, TinyLlama, and Huggingface Zephyr. 1.5-Pints demonstrates that by focusing on data quality over quantity in LLM training, we can significantly reduce training time and resources required. We believe this approach will not only make pre-training more accessible but also reduce our carbon footprint. Our findings and resources from this research are open-sourced, aiming to facilitate further advancements in the field. The 1.5-Pints model is available in two versions: 2K and 16K context windows.
|
https://arxiv.org/abs/2408.03506v1
|
This paper presents a scoping review of algorithmic fairness research over the past fifteen years, utilising a dataset sourced from Web of Science, HEIN Online, FAccT and AIES proceedings. All articles come from the computer science and legal field and focus on AI algorithms with potential discriminatory effects on population groups. Each article is annotated based on their discussed technology, demographic focus, application domain and geographical context. Our analysis reveals a growing trend towards specificity in addressed domains, approaches, and demographics, though a substantial portion of contributions remains generic. Specialised discussions often concentrate on gender- or race-based discrimination in classification tasks. Regarding the geographical context of research, the focus is overwhelming on North America and Europe (Global North Countries), with limited representation from other regions. This raises concerns about overlooking other types of AI applications, their adverse effects on different types of population groups, and the cultural considerations necessary for addressing these problems. With the help of some highlighted works, we advocate why a wider range of topics must be discussed and why domain-, technological, diverse geographical and demographic-specific approaches are needed. This paper also explores the interdisciplinary nature of algorithmic fairness research in law and computer science to gain insight into how researchers from these fields approach the topic independently or in collaboration. By examining this, we can better understand the unique contributions that both disciplines can bring.
|
https://arxiv.org/abs/2408.01448v1
|
The high-resolution echelle spectrograph UVES of the Very Large Telescope at
Cerro Paranal in Chile has been regularly operated since April 2000. Thus, UVES
archival data originally taken for astronomical projects but also including sky
emission can be used to study airglow variations on a time scale longer than a
solar cycle. Focusing on OH emission and observations until March 2015, we
considered about 3,000 high-quality spectra from two instrumental set-ups
centred on 760 and 860 nm, which cover about 380 nm each. These data allowed us
to measure line intensities for several OH bands in order to derive band
intensities and rotational temperatures for different upper vibrational levels
as a function of solar activity and observing date. The results were compared
with those derived from emission and temperature profile data of the radiometer
SABER on the TIMED satellite taken in the Cerro Paranal area between 2002 and
2015. In agreement with the SABER data, the long-term variations in OH
intensity and temperature derived from the UVES data are dominated by the solar
cycle, whereas secular trends appear to be negligible. Combining the UVES and
SABER results, the solar cycle effects for the OH intensity and temperature are
about 12 to 17% and 4 to 5 K per 100 sfu and do not significantly depend on the
selected OH band. The data also reveal that variations of the effective OH
emission layer height and air density can cause significant changes in the OH
rotational temperatures due to a varying ratio of OH thermalising collisions by
air molecules and OH radiation, deactivation, and destruction processes which
impede the rotational relaxation. However, this effect appears to be of minor
importance for the explanation of the rotational temperature variations related
to the solar activity cycle, which causes only small changes in the OH emission
profile.
|
http://arxiv.org/abs/1705.07239v1
|
We provide explicit combinatorial formulas for Ottaviani's degree 15
invariant which detects cubics in 5 variables that are sums of 7 cubes. Our
approach is based on the chromatic properties of certain graphs and relies on
computer searches and calculations.
|
http://arxiv.org/abs/1402.2669v2
|
A comparative the telescope twin P-E, one is in Observat\'orio Pico dos Dias,
Brazil, other in Observatoire Mont-M\'egantic, Qu\'ebec, Canada. The same
project, the same beginning configuration but different stories, different
solutions for the problems by the years.
|
http://arxiv.org/abs/1501.07333v1
|
By cryogenically cooling the Yb:YAG/Cr:YAG medium, one can break through the
damage limit of Yb:YAG/Cr:YAG passively Q-switched microchip lasers at room
temperature and thus achieve a shorter minimum pulse duration. In the proof of
principle experiment we carried out, a 160.6 ps pulse duration was obtained. To
the best of our knowledge, this is the first realization of sub-200 ps pulse
operation for an Yb:YAG/Cr:YAG microchip laser
|
http://arxiv.org/abs/1805.09471v1
|
We confirm by using the Skyrme Hartree-Fock-Bogoliubov calculation that $ {}^{164} \mathrm{Pb} $ is a possible heaviest $ N = Z $ doubly magic nucleus whose lifetime is long enough to be measured on accelerator experiments. We estimate the proton-emission and alpha-decay half-lives of $ {}^{164} \mathrm{Pb} $. The estimated proton-emission half-life ranges from $ 0.1 \, \mathrm{ps} $ to $ 10 \, \mathrm{ns} $, while the alpha decay can be safely neglected.
|
https://arxiv.org/abs/2405.12095v2
|
In this article, we proposed a programmable 16-channel photonic solver for quadratic unconstrained binary optimization (QUBO) problems. The solver is based on a hybrid optoelectronic scheme including a photonic chip and the corresponding electronic driving circuit. The photonic chip is fabricated on silicon on insulator (SOI) substrate and integrates high-speed electro-optic modulators, thermo-optic phase shifters and photodetectors to conduct the 16-dimensional optical vector-matrix multiplication (OVMM). Due to the parallel and low latency propagation of lightwave, the calculation of the QUBO cost function can be accelerated. Besides, the electronic processor is employed to run the heuristic algorithm to search the optimal solution. In the experiment, two 16-dimensional randomly generated QUBO problems are solved with high successful probabilities. To our knowledge, it is the largest scale of programmable and on-chip photonic solver ever reported. Moreover, the computing speed of the OVMM on photonic chip is ~2 TFLOP/s. It shows the potential of fast solving such optimization problems with integrated photonic systems.
|
https://arxiv.org/abs/2407.04713v1
|
We present some generalization of 16D oscillator by anisotropic and nonlinear
inharmonic terms and its dual analog for 9D related MICZ-Kepler systems by
generalized version of the Kustaanheimo-Stiefel transformation. The solvability
of the Schr\"{o}dinger equation of the these problems by the variables
separation method are discussed in different coordinates.
|
http://arxiv.org/abs/1903.10847v1
|
We present a linearly arrayed, 16-element, superconducting nanowire single-photon detector with 83.4$\%$ system detection efficiency at 1550 nm and a mean per-element dead-time of 9.6-ns, enabling counting at 1 giga-count per second with $>50\%$ System Detection Efficiency. This device was designed and fabricated in an existing scalable commercial process.
|
https://arxiv.org/abs/2103.14086v1
|
We propose a method to continuously frequency shift a target laser that is frequency stabilized by a reference laser, which is several hundreds of nanometers detuned. We demonstrate the technique using the 5S 1/2 to 5P 3/2 to 29D 5/2 Rydberg transition in 87Rb vapor and lock the 482 nm target laser to the 780 nm reference laser using the cascaded electromagnetically induced transparency signal. The stabilized frequency of the target laser can be shifted by about 1.6 GHz by phase modulating the reference laser using a waveguide-type electro-optical modulator. This simple method for stable frequency shifting can be used in atomic or molecular physics experiments that require a laser frequency scanning range on the order of several GHz.
|
https://arxiv.org/abs/2104.11423v1
|
Collisions of light and heavy nuclei in relativistic heavy-ion collisions have been shown to be sensitive to nuclear structure. With a proposed $^{16}\mathrm{O}^{16}\mathrm{O}$ run at the LHC and RHIC we study the potential for finding $\alpha$ clustering in $^{16}$O. Here we use the state-of-the-art iEBE-VISHNU package with $^{16}$O nucleonic configurations from {\rm ab initio} nuclear lattice simulations. This setup was tuned using a Bayesian analysis on pPb and PbPb systems. We find that the $^{16}\mathrm{O}^{16}\mathrm{O}$ system always begins far from equilibrium and that at LHC and RHIC it approaches the regime of hydrodynamic applicability only at very late times. Finally, by taking ratios of flow harmonics we are able to find measurable differences between $\alpha$-clustering, nucleonic, and subnucleonic degrees of freedom in the initial state.
|
https://arxiv.org/abs/2103.03345v1
|
We present calculations of various electroweak response functions for the 16O nucleus obtained using coupled-cluster theory in conjunction with the Lorentz integral transform method. We employ nuclear forces derived at next-to-leading order and next-to-next-to-leading order in chiral effective field theory and perform a Bayesian analysis to assess uncertainties. Our results are in good agreement with available electron-scattering data at q~ 326 MeV/c. Additionally, we provide several predictions for the weak response functions in the quasi-elastic peak region at q= 300 and 400 MeV/c, which are critical for long-baseline neutrino experiments.
|
https://arxiv.org/abs/2410.05962v1
|
Even though the main nucleosynthetic products of type Ia supernovae belong to
the iron-group, intermediate-mass alpha-nuclei (silicon, sulfur, argon, and
calcium) stand out in their spectra up to several weeks past maximum
brightness. Recent measurements of the abundances of calcium, argon, and sulfur
in type Ia supernova remnants have been interpreted in terms of
metallicity-dependent oxygen burning, in accordance with previous theoretical
predictions. It is known that $\alpha$-rich oxygen burning results from
$^{16}$O$\rightarrow^{12}$C followed by efficient $^{12}$C+$^{12}$C fusion
reaction, as compared to oxygen consumption by $^{16}$O fusion reactions, but
the precise mechanism of dependence on the progenitor metallicity has remained
unidentified so far. I show that the chain
$^{16}$O(p,$\alpha$)$^{13}$N($\gamma$,p)$^{12}$C boosts $\alpha$-rich oxygen
burning when the proton abundance is large, increasing the synthesis of argon
and calcium with respect to sulfur and silicon. For high-metallicity
progenitors, the presence of free neutrons leads to a drop in the proton
abundance and the above chain is not efficient. Although the rate of
$^{16}$O(p,$\alpha$)$^{13}$N can be found in astrophysical reaction rate
libraries, its uncertainty is unconstrained. Assuming that all reaction rates
other than $^{16}$O(p,$\alpha$)$^{13}$N retain their standard values, an
increase by a factor of approximately seven of the $^{16}$O(p,$\alpha$)$^{13}$N
rate at temperatures in the order $3-5\times10^9$ K is enough to explain the
whole range of calcium-to-sulfur mass ratios measured in Milky Way and LMC
supernova remnants. These same measurements provide a lower limit to the
$^{16}$O(p,$\alpha$)$^{13}$N rate in the mentioned temperature range, on the
order of a factor of 0.5 with respect to the rate reported in widely used
literature tabulations.
|
http://arxiv.org/abs/1907.01158v2
|
We calculate the $^{16}$O spectral function by combining coupled-cluster theory with a Gaussian integral transform and by expanding the integral kernel in terms of Chebyshev polynomials to allow for a quantification of the theoretical uncertainties. We perform an analysis of the spectral function and employ it to predict lepton-nucleus scattering. Our results well describe the $^{16}$O electron scattering data in the quasi-elastic peak for momentum transfers $|\mathbf{q}|\gtrapprox500$ MeV and electron energies up to 1.2 GeV, extending therefore the so-called first principles approach to lepton-nucleus cross sections well into the relativistic regime. To prove the applicability of this method to neutrino-nucleus cross sections, we implement our $^{16}$O spectral functions in the NuWro Monte Carlo event generator and provide a comparison with recently published T2K neutrino data.
|
https://arxiv.org/abs/2309.00355v1
|
The Semimicroscopic Algebraic Cluster Model (SACM) is applied to 16O, assumed
to consist of a system of four alpha-clusters. For the 4-alpha cluster system a
microscopic model space is constructed, which observes the
Pauli-Exclusion-Principle (PEP) and is symmetric under permutation of the
4-alpha-particles. A phenomenological Hamiltonian is used, justifying the name
Semi in the SACM. The spectrum and transition values are determined. One of the
main objectives is to test the importance of the Pauli Exclusion Principle
(PEP), comparing the results with the Algebraic Cluster Model (ACM), which does
not include the PEP, and claims that the 16O shows evidence of a tetrahedral
structure, which can be explained easily by symmetry arguments. We show that
PEP is very important and cannot be neglected, otherwise it leads to a wrong
interpretation of the band structure and to too many states at low energy.
|
http://arxiv.org/abs/1901.04883v2
|
Participating a scientific workshop is nowadays often an adventure because the number of participants do seldom exceed the number of talks. A half-day workshop is mostly finished at lunchtime, speakers are sometimes not present and unexcused, and a strict progression of the workshop offers little air for discussion. And when talks are re-scheduled on short notice in case that a speech is dropped out, attaining guests definitely wonder why the presenter is talking about something that does not match the previously announced talk. In this respect, we believe that the organization of a workshop in the classical sense must be reconsidered. It is not enough of compelling the presenters to pay the registration fee only and to let the participants being impassive or taken away mentally. With this work, we address several propositions to become implemented in the future workshop organization. With that, we hope to contribute to the identification of scientific workshops as a place of interaction.
|
https://arxiv.org/abs/0809.4916v1
|
We present a novel non-linear precoding technique for the transmission of 16
quadrature amplitude modulation (QAM) symbols in a 1-bit massive multi-user
(MU) multipleinput- single-output (MISO) downlink system. We deploy low
resolution digital-to-analog converters (DACs) at the transmitter for the sake
of decreasing the high energy consumption related to the massive MISO system.
To mitigate the multi-user interference (MUI) and the distortions due to the
low resolution DACs, the minimum bit error ratio (MBER) precoder was introduced
in previous work. However, this precoder technique is restricted to quadrature
phase shift keying (QPSK) signaling. Our approach consists in upgrading this
method to the transmission of 16 QAM symbols. Simulation results show that the
performance in terms of uncoded BER is significantly improved for larger
massive MISO gain.
|
http://arxiv.org/abs/1612.05286v1
|
Entanglement is an important evidence that a quantum device can potentially solve problems intractable for classical computers. In this paper, we prepare connected graph states involving 8 to 16 qubits on ibmqx5, a 16-qubit superconducting quantum processor accessible via IBM cloud,using low-depth circuits. We demonstrate that the prepared state is fully entangled, i.e. the state is inseparable with respect to any fixed partition.
|
https://arxiv.org/abs/1801.03782v3
|
We demonstrate for the first time the coexistence of a quantum-channel and 8x200 Gpbs 16-QAM optical channels with launching powers as high as -9dBm per channel in a 2 km HC-NANF. Comparative analysis with single-mode fibre reveals that the quantum channel could not be sustained at such power levels.
|
https://arxiv.org/abs/2106.14560v2
|
https://aclanthology.org/2020.isa-1.0
|
|
Galloping is a common high-speed gait in both animals and quadrupedal robots, yet its energetic characteristics remain insufficiently explored. This study systematically analyzes a large number of possible galloping gaits by categorizing them based on the number of flight phases per stride and the phase relationships between the front and rear legs, following Hildebrand's framework for asymmetrical gaits. Using the A1 quadrupedal robot from Unitree, we model galloping dynamics as a hybrid dynamical system and employ trajectory optimization (TO) to minimize the cost of transport (CoT) across a range of speeds. Our results reveal that rotary and transverse gallop footfall sequences exhibit no fundamental energetic difference, despite variations in body yaw and roll motion. However, the number of flight phases significantly impacts energy efficiency: galloping with no flight phases is optimal at lower speeds, whereas galloping with two flight phases minimizes energy consumption at higher speeds. We validate these findings using a quadratic programming (QP)-based controller, developed in our previous work, in Gazebo simulations. These insights advance the understanding of quadrupedal locomotion energetics and may inform future legged robot designs for adaptive, energy-efficient gait transitions.
|
https://arxiv.org/abs/2503.13716v1
|
The SPEC Power benchmark offers valuable insights into the energy efficiency of server systems, allowing comparisons across various hardware and software configurations. Benchmark results are publicly available for hundreds of systems from different vendors, published since 2007. We leverage this data to perform an analysis of trends in x86 server systems, focusing on power consumption, energy efficiency, energy proportionality and idle power consumption. Through this analysis, we aim to provide a clearer understanding of how server energy efficiency has evolved and the factors influencing these changes.
|
https://arxiv.org/abs/2411.07062v1
|
The Ulysses spacecraft provided the first opportunity to identify and study
Interstellar Dust (ISD) in-situ in the Solar System between 1992 and 2007. Here
we present the first comprehensive analysis of the ISD component in the entire
Ulysses dust data set. We analysed several parameters of the ISD flow in a
time-resolved fashion: flux, flow direction, mass index, and flow width. The
general picture is in agreement with a time-dependent focussing/defocussing of
the charged dust particles due to long-term variations of the solar magnetic
field throughout a solar magnetic cycle of 22 years. In addition, we confirm a
shift in dust direction of $50^{\circ} \pm 7^{\circ}$ in 2005, along with a
steep, size-dependent increase in flux by a factor of 4 within 8 months. To
date, this is difficult to interpret and has to be examined in more detail by
new dynamical simulations. This work is part of a series of three papers. This
paper concentrates on the time-dependent flux and direction of the ISD. In a
companion paper (Kr\"uger et al., 2015) we analyse the overall mass
distribution of the ISD measured by Ulysses, and a third paper discusses the
results of modelling the flow of the ISD as seen by Ulysses (Sterken et al.,
2015).
|
http://arxiv.org/abs/1508.03242v1
|
In the early 1990s, contemporary interstellar dust (ISD) penetrating deep
into the heliosphere was identified with the in-situ dust detector on board the
Ulysses spacecraft. Between 1992 and the end of 2007 Ulysses monitored the ISD
stream. The interstellar grains act as tracers of the physical conditions in
the local interstellar medium surrounding our solar system. Earlier analyses of
the Ulysses ISD data measured between 1992 and 1998 implied the existence of
'big' ISD grains [up to 10^-13kg]. The derived gas-to-dust-mass ratio was
smaller than the one derived from astronomical observations, implying a
concentration of ISD in the very local interstellar medium. We analyse the
entire data set from 16 yr of Ulysses ISD measurements in interplanetary space.
This paper concentrates on the overall mass distribution of ISD. An
accompanying paper investigates time-variable phenomena in the Ulysses ISD
data, and in a third paper we present the results from dynamical modelling of
the ISD flow applied to Ulysses. We use the latest values for the interstellar
hydrogen and helium densities, the interstellar helium flow speed of
v_ISM,inf=23.2km/s, and the ratio of radiation pressure to gravity, beta,
calculated for astronomical silicates. We find a gas-to-dust-mass ratio in the
local interstellar cloud of R_g/d=193^+85_-57, and a dust density of
2.1+/-0.6x10^-24kg/m^3. For a higher inflow speed of 26km/s, the
gas-to-dust-mass ratio is 20% higher, and, accordingly, the dust density is
lower by the same amount. The gas-to-dust mass ratio derived from our new
analysis is compatible with the value most recently determined from
astronomical observations. We confirm earlier results that the very local
interstellar medium contains 'big' (i.e. 1 um-sized) ISD grains. We find a dust
density in the local interstellar medium that is a factor of three lower than
values implied by earlier analyses.
|
http://arxiv.org/abs/1510.06180v1
|
High quality factor optical microcavities have been employed in a variety of
material systems to enhance nonlinear optical interactions. While
single-crystalline aluminum nitride microresonators have recently emerged as a
low loss platform for integrated nonlinear optics such as four wave mixing and
Raman lasing, few studies have investigated this material for second-harmonic
generation. In this Letter, we demonstrate an optimized fabrication of
dually-resonant phase-matched ring resonators from epitaxial aluminum nitride
thin films. An unprecendented second-harmonic generation efficiency of
17,000%/W is obtained in the low power regime and pump depletion is observed at
a relatively low input power of 3.5 mW. This poses epitaxial aluminum nitride
as the highest efficiency second-harmonic generator among current integrated
platforms.
|
http://arxiv.org/abs/1807.09638v3
|
Since ordered trees and Dyck paths are equinumerous, so are ordered forests
and grand-Dyck paths that start with an upwards step.
|
http://arxiv.org/abs/1608.08740v1
|
The frequency and phase fluctuations of free-running lasers limit the performance of optical heterodyne sub-THz systems - especially for low subcarrier spacing OFDM signals. Digital impairment compensation is implemented here for the successful generation of 170 - 260 GHz sub-THz OFDM signals over 10km analog-RoF link.
|
https://arxiv.org/abs/2309.16696v1
|
We report an industry leading optical dense wavelength division multiplexing (DWDM) field trial with line rates per channel exceeding 1.66 Tb/s using 130 GBaud dual-polarization probabilistic constellation shaping 256-ary quadrature amplitude modulation (DP-PCS256QAM) in a high capacity data center interconnect (DCI) scenario. This research trial was performed on 96.5 km of field-deployed standard single mode G.652 fiber infrastructure of Deutsche Telekom in Germany employing Erbium-doped fiber amplifier (EDFA)-only amplification. A total of 34 channels were transmitted with 150 GHz spacing for a total fiber capacity of 56.51 Tb/s and a spectral efficiency higher than 11bit/s/Hz. In the single-channel transmission scenario 1.71 Tb/s was achieved over the same link. In addition, we successfully demonstrate record net bitrates of 1.88 Tb/s in back-to-back (B2B) using 130 GBaud DP-PCS400QAM.
|
https://arxiv.org/abs/2108.01873v1
|
A full evaluation of the uncertainty budget for the ytterbium ion optical clock at the National Physical Laboratory (NPL) was performed on the electric octupole (E3) $^2\mathrm{S}_{1/2}\,\rightarrow\, ^2\mathrm{F}_{7/2}$ transition. The total systematic frequency shift was measured with a fractional standard systematic uncertainty of $2.2\times 10^{-18}$. Furthermore, the absolute frequency of the E3 transition of the $^{171}$Yb$^+$ ion was measured between 2019 and 2023 via a link to International Atomic Time (TAI) and against the local caesium fountain NPL-CsF2. The absolute frequencies were measured with fractional standard uncertainties between $3.7 \times 10^{-16}$ and $1.1 \times 10^{-15}$, and all were in agreement with the 2021 BIPM recommended frequency.
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https://arxiv.org/abs/2403.14423v1
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Chirped pulse amplification (CPA) has been adopted as a commonly used methodology to obtain powerful ultrashort laser pulses since its first demonstration. However, wavelength-tunable CPA systems are rarely reported. Wavelength-tunable ultrashort and intense laser pulses are desired in various fields like nonlinear spectroscopy and optical parametric amplification. In this work, we report a 1720 nm -1800 nm tunable CPA system based on a single-mode Tm-doped fiber covering the middle wavelength band of the third biological window. The tunable CPA system delivers ultrashort pulses varied between ~300 to 500 fs depending on the central wavelength emission at the fixed repetition rate of 22.7 MHz. The maximum average power ranges from 126 mW at 1720 nm to 294 mW at 1800 nm following the gain shape of Tm-doped fiber. Considering the specific wave-length range, this tunable CPA system is highly desired for biomedical imaging, sensing and parametric amplifiers for mid-infrared light generation.
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https://arxiv.org/abs/2312.06223v1
|
We reported the realization of a $^{174}\mathrm{Yb}^+$-$^{113}\mathrm{Cd}^+$ bi-species Coulomb crystal comprising $^{174}\mathrm{Yb}^+$ ions as coolant and verified its potential for application as a $^{113}\mathrm{Cd}^+$ microwave frequency standard employing sympathetic cooling.The two species of massive ions stably trapped in a Paul trap make up this large two-component crystal. The $^{113}\mathrm{Cd}^+$ ions are trapped in the center, which reduces considerably RF heating and excess micromotion to which the $^{113}\mathrm{Cd}^+$ ions are subjected. Under this scheme, the uncertainty due to the second-order Doppler effect is reduced to $5\times10^{-16}$, which represents an order of magnitude improvement over sympathetic cooled $^{40}\mathrm{Ca}^+$-$^{113}\mathrm{Cd}^+$ crystal. The uncertainty from the second-order Zeeman effect, which contributes the largest uncertainty to the microwave-ion frequency standard, is reduced to $4\times10^{-16}$. The relevant AC Stark shift uncertainty is estimated to be $4\times10^{-19}$. These results indicate using $^{174}\mathrm{Yb}^+$ as coolant ions for $^{113}\mathrm{Cd}^+$ is far superior and confirm the feasibility of a sympathetic-cooled cadmium-ion microwave clock system employing a $^{174}\mathrm{Yb}^+$-$^{113}\mathrm{Cd}^+$ two-component crystal.
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https://arxiv.org/abs/2307.01656v1
|
It has been suggested that centaurs may lose their red surfaces and become
bluer due to the onset of cometary activity, but the way in which cometary
outbursts affect the surface composition and albedo of active centaurs is
poorly understood. We obtained consistent visual-near-infrared (VNIR)
reflectance spectra of the sporadically active centaur 174P/Echeclus during a
period of inactivity in 2014 and six weeks after its outburst in 2016 to see if
activity had observably changed the surface properties of the nucleus. We
observed no change in the surface reflectance properties of Echeclus following
the outburst compared to before, indicating that, in this case, any surface
changes due to cometary activity were not sufficiently large to be observable
from Earth. Our spectra and post-outburst imaging have revealed, however, that
the remaining dust coma is not only blue compared to Echeclus, but also bluer
than solar, with a spectral gradient of -7.7+/-0.6% per 0.1 micron measured
through the 0.61-0.88 micron wavelength range that appears to continue up to a
wavelength of around 1.3 micron before becoming neutral. We conclude that the
blue visual color of the dust is likely not a scattering effect, and instead
may be indicative of the dust's carbon-rich composition. Deposition of such
blue, carbon-rich, comatic dust onto a red active centaur may be a mechanism by
which its surface color could be neutralized.
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http://arxiv.org/abs/1811.11220v3
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We experimentally demonstrate agreement between two $^{176}$Lu$^+$ frequency references using correlation spectroscopy. From a comparison at different magnetic fields, we obtain a quadratic Zeeman coefficient of $-4.89264(88)\,\mathrm{Hz/mT^2}$, which gives a corresponding fractional frequency uncertainty contribution of just $2.5\times 10^{-20}$ for comparisons at typical operating fields of 0.1\,mT. A subsequent comparison with both systems at 0.1\,mT, demonstrates a fractional frequency difference of $(-2.0\pm(3.7)_\mathrm{stat}\pm(0.9)_\mathrm{sys})\times10^{-18}$, where `stat' and `sys' indicate statistical and systematic uncertainty, respectively.
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https://arxiv.org/abs/2212.04652v1
|
This work aims to investigate the accuracy of quantitative SPECT imaging of $^{177}$Lu in the presence of $^{90}$Y, which occurs in dual-isotope radiopharmaceutical therapy (RPT) involving both isotopes. We used the GATE Monte Carlo simulation toolkit to conduct a phantom study, simulating spheres filled with $^{177}$Lu and $^{90}$Y placed in a cylindrical water phantom that was also filled with activity of both radionuclides. We simulated multiple phantom configurations and activity combinations by varying the location of the spheres, the concentrations of $^{177}$Lu and $^{90}$Y in the spheres, and the amount of background activity. We investigated two different scatter window widths to be used with triple energy window (TEW) scatter correction. We also created multiple realizations of each configuration to improve our assessment, leading to a total of 540 simulations. Each configuration was imaged using a simulated Siemens SPECT camera. The projections were reconstructed using the standard 3D OSEM algorithm, and errors associated with $^{177}$Lu activity quantification and contrast-to-noise ratios (CNRs) were determined. In all configurations, the quantification error was within $\pm$6% of the no-$^{90}$Y case, and we found that quantitative accuracy may slightly improve when $^{90}$Y is present because of reduction of errors associated with TEW scatter correction. The CNRs were not significantly impacted by the presence of $^{90}$Y, but they were increased when a wider scatter window width was used for TEW scatter correction. The width of the scatter windows made a small but statistically significant difference of 1-2% on the recovered $^{177}$Lu activity. Based on these results, we can conclude that activity quantification of $^{177}$Lu and lesion detectability is not degraded by the presence of $^{90}$Y.
|
https://arxiv.org/abs/2301.10870v1
|
Fission at low excitation energy is an ideal playground to probe the impact of nuclear structure on nuclear dynamics. While the importance of structural effects in the nascent fragments is well-established in the (trans-)actinide region, the observation of asymmetric fission in several neutron-deficient pre-actinides can be explained by various mechanisms. To deepen our insight into that puzzle, an innovative approach based on inverse kinematics and an enhanced version of the VAMOS++ heavy-ion spectrometer was implemented at the GANIL facility, Caen. Fission of $^{178}$Hg was induced by fusion of $^{124}$Xe and $^{54}$Fe. The two fragments were detected in coincidence using VAMOS++ supplemented with a new SEcond Detection arm. For the first time in the pre-actinide region, access to the pre-neutron mass and total kinetic energy distributions, and the simultaneous isotopic identification of one the fission fragment, was achieved. The present work describes the experimental approach, and discusses the pre-neutron observables in the context of an extended asymmetric-fission island located south-west of $^{208}Pb. A comparison with different models is performed, demonstrating the importance of this "new" asymmetric-fission island for elaborating on driving effects in fission.
|
https://arxiv.org/abs/2211.01879v1
|
Tantalum-180m is nature's rarest (quasi) stable isotope and its astrophysical origin is an open question. A possible production site of this isotope is the slow neutron capture process in Asymptotic Giant Branch stars, where it can be produced via neutron capture reactions on unstable $^{179}$Ta. We report a new measurement of the $^{179}$Ta($n,\gamma$)$^{180}$Ta cross section at thermal neutron energies via the activation technique. Our results for the thermal and resonance-integral cross-sections are 952 $\pm$ 57 b and 2013 $\pm$ 148 b, respectively. The thermal cross section is in good agreement with the only previous measurement (Phys. Rev C {\bf 60} 025802, 1999), while the resonance integral is different by a factor of $\approx$1.7. While neutron energies in this work are smaller than the energies in a stellar environment, our results may lead to improvements in theoretical predictions of the stellar cross section.
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https://arxiv.org/abs/2304.06799v1
|
High-speed active metasurfaces enable spatiotemporal control of incident light within an ultra-thin layer, offering new possibilities for optical communication, computing, and sensing. However, a fundamental tradeoff between electrical conductivity and optical absorption of the material has hindered the realization of active metasurfaces that simultaneously achieve broad modulation bandwidth and low optical loss. Here, we experimentally demonstrate a high-speed active metasurface operating in the 1.5-{\mu}m wavelength range that realizes a record-high modulation bandwidth of 17.5 GHz, while maintaining a high quality (Q) factor of 102 and an ultra-low optical loss of 0.56 dB. The key enabling technology is the indium-phosphide (InP) membrane platform; an n-type InP offers both high electron mobility and low free-carrier optical absorption, making it an ideal material for active metasurface devices. The high-Q Friedrich-Wintgen quasi-bound-states-in-the-continuum mode inside the InP-membrane high-contrast grating (HCG) is utilized to trap the normally incident light within an organic electro-optic (OEO) material, enabling efficient modulation. InP HCG also serves as an ultralow-resistance interdigitated electrodes for applying high-speed electrical signals to the OEO material, thereby offering 50-fold improvement in modulation bandwidth compared to conventional silicon-based counterparts. Our work paves the way towards high-speed, low-loss active metasurfaces for spatiotemporal control of light beyond the gigahertz regime.
|
https://arxiv.org/abs/2505.07072v1
|
For many years, various experiments have attempted to shed light on the nature of dark matter (DM). This work investigates the possibility of using CaWO4 crystals for the direct search of spin-dependent DM interactions using the isotope 17O with a nuclear spin of 5/2. Due to the low natural abundance of 0.038%, an enrichment of the CaWO4 crystals with 17O is developed during the crystal production process at the Technical University of Munich. Three CaWO4 crystals were enriched, and their 17O content was measured by nuclear magnetic resonance spectroscopy at the University of Leipzig. This paper presents the concept and first results of the 17O enrichment and discusses the possibility of using enriched crystals to increase the sensitivity for the spin-dependent DM search with CRESST.
|
https://arxiv.org/abs/2311.03161v1
|
We prove that the transitive permutation group 17T7, isomorphic to a split extension of $C_2$ by $\mathrm{PSL}_2(\mathbb{F}_{16})$, is a Galois group over the rationals. The group arises from the field of definition of the 2-torsion on an abelian fourfold with real multiplication defined over a real quadratic field. We find such fourfolds using Hilbert modular forms. Finally, building upon work of Demb\'el\'e, we show how to conjecturally reconstruct a period matrix for an abelian variety attached to a Hilbert modular form; we then use this to exhibit an explicit degree 17 polynomial with Galois group 17T7.
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https://arxiv.org/abs/2411.07857v2
|
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